qpms/tests/tbeyn.c

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#include <qpms/beyn.h>
#include <stdio.h>
// Matrix as in Beyn, section 4.11
int M_function(gsl_matrix_complex *target, complex double z, void *no_params) {
int m = target->size1;
gsl_complex d = gsl_complex_fromstd( 2*m - 4*z / (6*m) );
gsl_complex od = gsl_complex_fromstd( -m - z / (6*m) );
gsl_matrix_complex_set_zero(target);
for (int i = 0; i < m; ++i) {
gsl_matrix_complex_set(target, i, i, (gsl_complex) d);
if(i > 0) gsl_matrix_complex_set(target, i, i-1, (gsl_complex) od);
if(i < m - 1) gsl_matrix_complex_set(target, i, i+1, (gsl_complex) od);
}
return 0;
}
int main() {
complex double z0 = 150+2*I;
double Rx = 148, Ry = 148;
int L = 10, N = 50, dim = 400;
BeynSolver * solver = CreateBeynSolver(dim, L);
int K = BeynSolve(solver, M_function, NULL /*M_inv_Vhat_function*/, NULL /*params*/,
z0, Rx, Ry, N);
printf("Found %d eigenvalues:\n", K);
for (int i = 0; i < K; ++i) {
gsl_complex eig = gsl_vector_complex_get(solver->Eigenvalues, i);
printf("%d: %g%+gj\n", i, GSL_REAL(eig), GSL_IMAG(eig));
}
DestroyBeynSolver(solver);
return 0;
}